Motor controller



R. G. LOCKETT MOTOR CONTROLLER Filed Jan. 50. 1922 N S en "0 i: i@ O r *9 d' @Y N N N N N E'L i?. l" S :n T C 0F 2 I- e s Y. ro

11h n M n INVENTOR.

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ATTORNEY Patented Jan. l, 1924.

UNITED STATES 1,419,001 PATENT jor-'r-ici:.;

RALPH G. LOCKETT, OF MILWAUKEE, WISCONSIN, ASSIGNOR T0 `THB.' CUTLEB-HAMMER MFG. CO., OF MILWAUKEE, WISCONSIN, A CORPORATION 0F WISCONSIN.

Moron coN'rnoLLEa .Application med January 80, 1922. Serial Fc. 532,605.

To all whom it may concern:

.Be it known that I, RALPH G. Locxn'rr, a citizen of the United States, residing at Milwaukee, in the county of Milwaukee and State of Wisconsin, have invented new and useful Improvements in Motor Controllers, of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawing, forming a art of this specification.

his invention `relates to improvements in motor controllers.

While not limited thereto the invention is particularly applicable to controllers for motor driven extractors and other machines having a high moment of inertia, where the motor'` is employed to bring the extractoror other machine to rest by the dynamic braking action of such motor. As will be understood the shunt field of the motorl must be protected against overheating when the motor is at rest, while on the other hand it is highly desirable to maintain full excitation ofthe shunt field until the motor and its associated machine are brought to a standstill as yotherwise the stopping is prolonged due to cessation of the braking action of the motor.4

Such prolonged and uncertain stopping periods are very undesirable in many instances particularly in extractor control and the present invention has among its objects to provide a 'controller embodying simple and efficient means toinsure full shunt field strength until the motor and its associated machine' are brought to a standstill by the dynamic braking action of the former while at the same time insuring rotective commutation of the shunt fi ld connections promptly upon arrest of themotor.

Another object is to provide such a controller wherein the means functioning to maintain full field strength during dynamic braking also functions to insure full field strength for starting and moreover tends to maintain full shunt field strength of the ynamic motor during the transition from runningv connections to dynamic braking connections.

Another object is to provide a. controller embodying shunt field controlmeans func` tioning as stated and `providing for interruption of the shunt field circuit when the motor is stopped.

Another object is to provide a controller embodying means of the aforesaid character period functionin either with or without the fore` going resu ts to control safety orvindicating devices and particularly to effect operation thereof when but not until themotor is brought to rest. l

Various other objects and advantages of the invention will. hereinafter appear.

The accompanying drawing diagrammatically illustrates a controller embodyin the invention in one form'` and the same wi now be described, it being understood that the embodiment illustrated is susceptible of various modifications without departing from the scope of the appended claims.

The controller illustrated is articularly7 designed for extractor control, t e extractor to be driven by a suitable motor, such as the motor M illustrated which has an armature a, a seriesnfield f and a shunt field f. This motor is shown as supplied from a di'- rect current supply line- Z-l through a knife switch 1 and electromagnetic Switches 2 and 3.

The switch 2 controls the continuity of the armature and series fieldV circuit of the motor, said switch being of the double throw type and normally standing in a position to interrupt said circuit. When. in such position the switch 2' completes a (Il)A dynamic braking circuit for the motorcom- '85 4winding fw and a series winding fw' The former winding is so controlled as to operate the switch immediately upon response of switch 2 and is maintained energized throughout the running period whereby connection of the shunt field is insured for starting and running. During dynamic braking the winding w is connected across the motor armature and the same is so designed as to hold the switch closed until the motor is brought practically to a standstill. Accordingly this windin which is connected directly across theine during running requires protection and to this end the same has includedin series therefwith a resistance r and also preferably has`A connected in shunt therewithl a resistance 1f". On ,the

\ of the series winding @of which is included in series in the dynamic braking circuit and which acts cumulativcly with the shunt winding to hold the switch 3 closed for dynamic braking. AS will hereinafter appear, means are preferably provided for graduating the dynamic braking action of the motor to maintain a high mean value of the braking current whereby reduction of the resistance of the circuit of the shunt winding w may be delayed until completion of the operation o such graduating means. Accordingly such means may be, and preferably is, employed to exclude the resistance at an appropriate time whereby the Windin in is rendered effective to a maximum dtegree for retaining the switch 3 `in closed position and it has been found that a relay of the type shown when controlled as described may be designed in ac cordance with well known principles to maintain the continuity of the shunt field circuit until the motor is brought practically to a standstill. Thereupon the supply of current from the motor to the relay windings i's terminated thus causing said relay to promptly release and disconnect the shunt field from circuit.

As will hereinafter appear, the circuit connections of the winding w of switch 3 are such that said winding is subjected to the E. M. F. of the motor during transition from running connections to dynamic braking connections and accordingly said s winding tends to inaitain the relay energized to maintain continuity of the shunt iield circuit during such transition. It will therefore bc apparent that by proper design of the controller the continuity of the lshunt field circuit may be definitely maintained during the transition period.

More speciiically considering the system illustrated` the motor is started with re,- sistunces R and R in series with its armature, said resistances being adaptedto be sequentially excluded from circuit by socalled lockout switches 4 and 5 respectively as the motor accelerates. The resistance R is'also arranged for inclusion in the dynamic braking circuit ot the 'motor together with additional resistances R2 and R and said resistances R andRl are arranged to he ex eluded from circuit sequentiaily'under given current conditions to maintain the braking current at a high mean value. The resistance R is so excluded by the switch 4 while the resistance R2 is so excluded by a. socalled lockout switch 6.

Each of the switches 4, 5 and 6 has a series operating Winding w and a series lockout winding wz, the latter functioning as is well understood to prevent response of its respective switch so long as the niotor current exceeds a given value. Further the switches 5 and 6 are each provided with a shunt winding fw, to act cumulatively with vits series operating winding, each switch being designed to require cumulative action of its windings for operation thereof. The shunt winding te of switch 5 is under the conti-ol of auxiliary contacts 2l oi the main switch 2 while, the shunt winding fw of switch (i is under the control of an electroresponsive relay 7. Switch 6, which is the lust to respond for graduation of the dynamic braking action of the motor, has auxiliary contacts 6 to shunt the resistance 1" for increasinlr the etlcctivcness of the shunt field switc 8 as heretofore set forth.

The relay 7 has a series operating winding w which is included in the dynamic braking circuit of the inotor and a shunt holding winding w, the circuit of which is completed upon response ot said relay. 'lliis relay normally interrupts the circuit of the shunt winding of switchr thereby insuringr against response of said switch except when the motor is acting as A a dynamic brake. Also this relay has norniallypclosed contacts 7 in series with the shunt winding Vuw otmain switch 2 and auxiliary contacts 7" in series with the coil 8 of a safety device.

The circuit of the coil 8 is completed by auxiliary' contacts 3 of the field controlling switch 3 when released and said coil under thc control of said switch and relay may be employed to trip the cover latch oi the extractor or to perform any other desired function when but not until the motor is brought to rest. The auxiliary contacts ot' switch 3 arealso utilized to complete the circuit of a lainp 9 when the motor is brought to a standstill.

For controlling theaforementioned instiunientalities there are provided a starting switch 11, a stopping switch l2 and a safety switch 123. The switches 1l and l2 are of the push button type, the former being normally open and the latter nor nially closed. The switch 13 which is normally open may be arranged to be closed by closure of the extractor cover or the saine may be associated with any preferred part of thedriven mechanism.

`When the switches 13 and l1 are closed,

circuit may be traced from line l through said switches and through sto switch 12 by conductor 15' to and throng the winding of main switch 2 by conductor 16 through the contacts 7` of relay 7 by conductor 17 lto linel. This eiects response of main switch 2 and upon response thereof ling, and closure of main switch 2 additionally completes the circuit of the motor armature and series field. Also response of main switch 2 connects resistance r inv shunt with the winding w, of switch 3, this shunt extending from the right hand terminal of said winding by conductors 20 and 22 through resistance- 7" to and throu h the auxiliary contacts 2 of main switc 2 by conductors 18 and 19 to the opposite terminals of said winding.

The shunt field circuit of the motor may then be traced from line l by conductor 23 through 'switch 3 by conductor 24 through said shunt field to line l. On the other hand switch 2 completes circuit from line l by conductor 18 to and through the motor armature by conductor 25 to and through the lockout winding of switch 5 by conductor 26 to and through the lockout wind- 'l ing of switch 6 by conductor 27 to and through the operating and lockout windingsot' switch i` and the resistances R and R in sci-ics by conductors `28 and 29 to and through the series Held f to line l. These connections manifestly render the switch 4 responsive subject to delay by excessive current conditions in the motor circuit.

Switch 4 in responding completes. circuit Jfrom a point intermediate its operating and lockcut windings by, conductor 30 to and through the series winding w of switch 6 by conductor 31 through the series operating winding of switch 5 and thence by conductor 32 to `a point between resistances R and R'. This excludes the resistance R from the motor circuit and includes in circuit the operating winding w of switch whereupon said switch is rendered responsive subject to delay by excessive current conditions in the motor circuit. -lVl1en switch 5 responds it completes circuit from the right hand terminal ot' thc motor-armature direct to conull ductor 29 thereby short-circuiting resistance R and also shortcircuiting the operating winding of switch 4 and its own operating winding.` Switch 4 is thus released to be inl readiness for dynamic braking (but the switch 5 is held closed by its winding w the circuit of which extends from auxiliary contacts 2 of main switch 2 by conductor 33 to and through said winding by conductor Mito and through the stop switch and thence through the operating winding of switch 2 as already traced. This circuit also obviously'constitutes a Amaintaining circuit for the main switch 2.

Assuming now that the push button 12 is depressed, it will be apparent that both the switch 5 and the main switch 2 will be deenergized, thus reinserting in the motor cir: cuit ltheresistances R and R and interrupting the power connections of tle motor armature, the switches being designed to effect these commutations progressively in the or- .der named. Also it will be obvious that such operation of the main switch 2 will complete the dynamic braking circuit of th'e motor which may be traced from the left hand terminal of t e motor armature by. conductor 18 to and through the down contacts of switch 2 by condu-ctor35 through the winding w of relay 7 by conductor 36 through winding w' of switch 3 by conductor 37 to and through resistances R, R2 and R in series and thence through both windingsof switch 4. by `conductr 27 through the lockout winding of switch 6 by conductor 26 to and through the lockout winding of switch 5 to conductor 25 leading to the right hand terminal of the motor armature. f

Also when power connections are interrupted circuit may be traced from the left hand terminal of the motor armature by conductors 18 and 19 through the shunt winding w of the field switch 3 by conductors 20 and 21 through resistance r by conductor 17 to the left hand terminal of the series field which has its right hand terminal connected to the right hand terminal of ther-motor armature as above described. Thus the winding w of the switch 3 is subjected to the E. M. F. of the motor during the transition period and if properly designed will hold the switch 3 closed to maintain the continuity of the shunt field circuit. Moreover` as soon as lthe braking circuit is completed the winding w of switch 3 is energized by the braking current to act cumulatively with the winding w to hold switch 3 closed. i l

'As will be apparent from the above description of the braking circuit the switch 4 has both of its windings connected in said circuit whereby upon reduction of the braking current to a given value said switch will respond to exclude from circuit the resistance R. The braking circuit will then extend from the right hand terminal of resistance R2 by conductor 32 to and through the winding fw of switch 5 by conductor 31 to and through the winding w' of switch 6 by conductor 30 to and through switch'4 and its operating winding by conductor 27 to and through the Olockout Vwint-linge of Switches 6 `and 5 and thence to the right lim terminal of the motor armature. This enmmutation oi connections subjects the Winding -zc of switch G to the braking current for action curnulatively with the Winding 'w of said switch the latter Winding being` energized by closure of relay 7. More specifically. upon closure of relay 7 circuit is completed from line Z through safety switch 13 by conductor d() to and through the Winding u of switch 6 by conductor 41 to and through the winding vo of switch 'i' and thence through the main contacts of said switch to line Z. .Mfcordingly when the braking current is again reduced to a. given value the switclr tl is caused to respond tio shortecircuit the resistance R2. The braking circuit then extends from a point between resistances R3 and Rf to and through switch 6 by conductor 26 to and through the lockoutcoil of switch by conductor 25 to the right, hand terminal of the motor armature. 'The resistance of' the braking circuitV is thus reduced to ed'ect stopping of the motor Without further resistance commutations although it will of course be understood that the resistance may in practice be excluded in any preferredv number' of steps.

` Moreover response-of switch G completes a circuit from the right hand terminal of the shuntv winding fui of switch 3 by conductors 20 and Q2 through the auxiliary contacts 6 of switch 6 to conductor 26 and thence through the lockout winding of switch 5 to the right hand terminal of the motor thus placing said winding w across the terminals of the motor armature exclusive of the resistance 1'. While as shown the resistance r is excluded in a single step it will of courseA he apparent that the same might be excluded in a number of .st-eps controllable by different, decelerating switches. Also it will be understood that by properly designing the Winding vr the same may. when so connected across the motor armature. be caused to hold the switch 3 closed until the motor is brought practically to a standstill, even though the winding zo is in the meantime practically deenergized by reduction of the braking current.

dien the switch 3 is finally Vreleased a circuit may he traced from line Z hy conductor Q?, to and through the auxiliary contacts 3a of' said switch hy conductor 42 to and through the coil S of the safety device by conductor 43 to and through the auxiliary contacts Tb of relay 7 by conductor 17 to line l. Also a parallel circuit may he traced from conductor 42 to the lamp 9 by conductors 44 and i7 to line l. Thus both of the instrumentalities 8 and tl are energized when but not until the motor is brought practically to a. standstill and the lamp 5l is maintained energized until the motor is restarted, However. the coil 8 is' dc-energized upon opening of the safe switch 13 which interrupts the circuit of the coils 'w of switch 6 and relay 7, said relay 7 in turn interrupting the circuit` of coil 8.

that I claim as new and desire to secure by Letters Patent is:

L In a controller for a motor driven machine in combination, stopping means, an electro-responsive device to be energized throughout operation of the driven machine and to be fle-energized upon stopping thereof, said device having an energizing Winding designed for relatively i'ow voltage and connections subjecting the same to the E. M. F. of the motor. protective resistance included in circuit with said winding and means for excluding said resistance from the circuit of said awinding as the motor is slowed down.

2. In a dynamic braking controller for a motor having a shunt field.y in combination, an electromesponsive switch for controlling the shunt field strength of the mo tor. said switch having an energizing windlng designed for relatively low voltage and Vconnections subjectingr the same to the E. M. F. of the motor, protective resistance included in circuit with said Winding and means for excluding said resistance trom the circuit of said Winding as the motor is slowed down.

il. In a d namic braking controller for a motor having a shunt field, in combination, an electro-responsive switch for controlling the shunt field strength of the Inotor, said switch having a Winding for connection in series in the braking circuit of the motor and a winding designed for relatively low voltage and having connections independent of the former winding for subjecting the same to the E. M. F. of the motor, protective resistance included in circuit with said low voltage winding and means for excluding said resistance from the circuiti as the motor is slowed down.

4. his dynamic braking controller for a motor having a shunt field. in combina tion, means for establishing a` dynamic breaking circuit for the motor including resistance and decreasing said resistance as the motor slows down, an electro-responsive switch to control the shunt field strength of 'the motor, said switch having an eherglzmg Winding designed for relatively low voltage and having connections subjecting the same to the E. M. F. of the motor. and a protective resistance for said winding having connections whereby the same is eX- cluded from the circuit of said winding by said means.

In a dynamic braking controller for a motor having a shunt field. in combination.` an electro-responsive switch to control the shunt field strength of the motor. said switch having en energizing Winding and" connections subjecting the same the E. M. F. of the motor, protective resistance normally included in circuit with said windingi and automatic means effecting graduate dynamic braking of the inotor and exclusion of said protective resistance from the circuit of said switch winding upon slow down of the motor.

6. In a dynamic braking controller for a motor having a shunt field, in combination, means for establishing dynamic braking connections for the motor including resistance and for varying such resistance, a switch controlling the shunt field strength of the motor, said switch having a Winding for4 inclusion in said dynamic braking oonnections and a winding independently connected to the motor to be subjected to the E.

M. F. thereof, and a protective resistance for the latter winding having connections subjecting the same to control by said means for exclusion thereof from `circuit whereby said switch is caused maintain a high shunt field strength until themotor is brought practically to a standstill.

7 In a controller for a motor having a shunt field, the combination with an electro-responsive switch to control the motor shunt field, said switch having an energizing winding designed for relatively low voltage and having protective resistance thereforof means to control the motor for running and dynamic braking including means to connect said switch winding through its protective resistance tofthe motor supply ci'rcuitfor running' and to subject/said switch winding exclusive ofits protective resistance to -the E.' M. F. of said motor for finaldynamic braking.

8. In a controller for a motor having a shunt field, the combination'with an electric switch to control the shunt field strength of the motor, said switch having' motor for running and dynamic braking in cliiding a switch to connect said winding to the motor supply circuit for running and a protective resistance for said windin also controlledyby said means to be ex iided from circi'iitthereby for causing said switch to maintain a hi hfshunt field strength until the motor is roughtpractically to a standstill. f

9. In a controller for a motor having a shunt field to be protectedwhile the motor is idle, the combination with an electro-re sponsive switch serving when dre-energized to protect the motor shunt field and responn sive to strengthen th`e latter, said 1." having an energizing winding desig relatively low voltage and permanently ceiiected to the motor to be subjected to the E. M. F. thereof and further having a pro- -cally' to a standstill.

tective vresistance normally in series with said winding, of means to control the inotor for running and dynamic braking including means to connect said winding to the motor supply circuit through said resistance foi running and to exclude said resistance from the motor connections of said winding as the motor is slowed down by its dynamic braking action.

10. In a controller for-a motor having a shunt field to be protected when the motor is idle, the combination withan electro-responsive switch servin when desenergized to protect the motor fie d and res onsiveto strengthen the latter, said switch aving an energizing winding designed for relatively low voltage, protective resistance therefor and permanent circuit connections subjecting said winding to the E. M. F. of the motor through said resistance, of an additional protective resistance for said winding and means to control the motor for running and dynamic braking including means whereby said -windinghis connected to the motorsiipply circuit t rough the first mentioned resistance land shunted by the .second mentioned resistance for running and whereby upon interruption of the motor su ply circuit, said windin is disconnected rom vthe second mentione protective resistance for dynamic braking an'd subsequently connected directly 0o the motor exclusive of the first mentioned resistancev for causing said switch to maintain a hi h shunt field strength until the motor is Arought practi- 11. In a controller for a motor having a shunt field, in combinatiommeans for establishing running vand dynamic braking connections for the motor armature, a switch to control the motor field and to s tnen hen the same 'for running and dynamic raking, said switch havin a winding to be included in the ldynamic brakiii circuit of the motor, a winding designed or relatively .low voltage and a protective resistance for the latter winding, permanent connections sai resistance to the E. F. of the motor and connections controlled by said means whereby said low voltage winding is connectedto the supply line throughsaid protective resistance for running and whereby said resistance is excluded from the ermanent connections of said winding as t e inosub'ecting said low voltageI winding through namic braking, said switch having a. wind- -ng for inclusion in the dynamic braking circuit of the motor, a winding designed for relatively low voltage and a protective resistance for the latter, permanent connections for said low voltage Winding subjecting the same through said protective resistance to the E. M. F. of the `motor and connections controlled by said means whereby said low voltage winding is connected to the motor supply circuit through said resistance for running and whereby said protective resistance is excluded from the permancnt connections of said low voltage winding during final braking action of the motor.

13. In a controller for a motor driven machine in combination, stopping means, means to function upon arrest of the machlne, an

electro-responsive controlling device for the sistance normally included in circuit with said winding and means for excluding said resistance from the circuit of said Winding as the motor is slowed down whereby said Winding is maintained energized until the motor is brought substantially to rest.

In witness whereof, I have hereunto subscribed my name.

RALPH G. LOCKETT. 

